Such pressure sensors include, as a rule, a measuring unit with two chambers, each of which is sealed by a separating membrane, or diaphragm, and filled with a transmission medium. The separating membranes are loaded, respectively, with a pressure being measured and with a reference pressure. These pressures are transmitted via the separating membranes into the respective chambers. The chambers are separated from one another by a sensor element in the form of a pressure sensitive element, especially a measuring membrane, which is loaded on its first surface with the hydraulic pressure in the first half-cell and on its second surface with the hydraulic pressure in the second half-cell.
The present invention relates to a relative pressure sensor with hydraulic pressure transmission. Such pressure sensors include, as a rule, a measuring unit with two chambers, each of which is sealed by a separating membrane, or diaphragm, and filled with a transmission medium. The separating membranes are loaded, respectively, with a pressure being measured and with a reference pressure. These pressures are transmitted via the separating membranes into the respective chambers. The chambers are separated from one another by a sensor element in the form of a pressure sensitive element, especially a measuring membrane, which is loaded on its first surface with the hydraulic pressure in the first half-cell and on its second surface with the hydraulic pressure in the second half-cell.
The second (atmosphere-side) separating membrane serves, on the one hand, for temperature compensation of the first degree in the case of small measuring ranges, and, on the other hand, for the “second-containment”, i.e. for additional protection of the environment of the device in the case of malfunctions, e.g. rupture of the first (process-side) separating membrane and/or the measuring membrane.
Especially pressure-sensitive elements of semiconductor materials have a stiffness such that the volume stroke at the pressure-sensitive element is practically negligible over the entire measuring range. This means, however, negatively, that the pressure-sensitive elements are very sensitive to needle-like pressure spikes, since scarcely any elasticity is present for absorbing such, so that a destruction of the measuring cell can result. By simple lessening of the diameter of the pressure supply line between the process-side chamber and the pressure-sensitive element, the needle pulses cannot be effectively damped, or attenuated.
German Offenlegungsschrift (laid-open application) DE 37 13 236 A1 discloses, instead, the installing, between process and the measuring cell, of a sintered metal plate, or a steel plate with one bore, or a plurality of parallel bores, of, at most, 0.5 mm diameter. This solution is not satisfactory for various reasons. On the one hand, the reduction of the hydraulic path between process and measuring cell to even a single bore of 0.5 mm diameter and bore length such as is to be expected from the shown plate thickness, offers, by far, no sufficient damping for suppressing needle-shaped, overloading, pressure spikes. On the other hand, if a damping element of a sufficiently great flow resistance for an effective damping is provided, then the reaction velocity of the sensor is significantly slowed, so that then pressure fluctuations within the measuring range of the sensor are registered only with delay.